This invention relates to an apparatus for recording and reproducing a signal on a disc type recording medium. More particularly, this invention relates to an apparatus of this type capable of monitoring recording data instantaneously during a recorded mode or editing recorded data with standard recording and reproducing heads. The invention relates also to an apparatus of this type capable of recording and reproducing a four-channel signal with recording and reproducing heads for a two-channel signal. The invention relates also to an apparatus of this type capable of dubbing data read from a reproducing optical disc to a recording optical disc with a set of a recording magnetic head and a recording and reproducing optical head.
Since a Compact Disc was developed as a superior recording medium to an analog record, some other new recording media have been developed. A Mini Disc (MD) is one of these newly developed recording media. The Mini Disc is attracting attention of the industry as a prospective audio reccording medium which has portability of the Compact Cassette and also operability and tone quality of the Compact Disc.
Since the MD has adopted a new audio compression system while employing the PCM system similar to the CD, the MD can realize a high tone quality which is about the same as the CD with the amount of information which is about half of the CD. For this reason, reproduction time which is about the same as the CD can be realized with a disc having a diameter which is about half that of the CD.
There are two types of MDs. One of them is a reproduction only MD which is made of an optical disc similar to the CD. The other type of MD which is capable of both recording and reproduction is made of a magneto-optical disc. An MD player adapted to these two types of MDs has not only an optical head for recording and reproduction but also a magnetic head for recording.
An MD player capable of both recording and reproduction has a recording mode in which the MD player writes data to be recorded on a disc and also a reproduction mode in which the MD player reads reproduced data from the disc. The user selects one of these modes in using the MD player.
For confirming instantaneously whether or not input data is accurately recorded while the input data is being recorded during the recording mode, the MD player must have a monitoring function. This monitoring function is different from a normal reproduction mode function because it is necessary to read out and reproduce recorded data instantaneously while the selected mode is the recording mode.
In the case of the MD player, reading of reproduced data is made with an optical head. This optical head can be used in the reading mode also in case a magneto-optical disc is mounted in the player. If, therefore, it is desired to monitor recording instantaneously during the recording mode, another optical head for the monitoring purpose will be required.
If, however, an extra optical head for monitoring is mounted in the MD player, a peripheral circuit (including an automatic laser beam control circuit and a servo control circuit) will also be required with the result that the structure of the MD player becomes complex and the manufacturing cost will naturally increase. Particularly, it is not desirable for an MD player for which portability is an important factor to be unable to realize a compact type MD player due to complexity of the structure and increased number of component parts.
It is, therefore, a first object of the invention to provide an apparatus for recording and reproducing a signal on a disc type recording medium capable of monitoring recording instantaneously with only a set of standard recording and reproducing heads without requiring an extra optical head for the monitoring purpose.
There is a case where music data which has once been recorded is subsequently processed and edited. In this case, there is required an editing mode using both the recording mode and the reproduction mode. A normally expected editing function includes overdubbing according to which recorded data is read out and, after new music data is added to a part of the read out data, is recorded again, so-called pingpong recording according to which plural recorded data are mixed and then recorded again, and punch-in/punch-out recording according to which a part of recorded data is changed to new music data.
For performing editing function by a conventional MD player, it is conceivable either (1) to reproduce data from an original disc by the MD player for reproduction and then recording data after editing on a recording disc by another recording player or (2) to provide an optical head for reproduction and a magneto-optical head for recording in a single player and perform reproduction and recording after editing on the same disc in real time.
In the two player system of (1) above , however, the player for reproduction only must be provided for the sole purpose of editing and this is apparently inefficient. This system is also disadvantageous in that edited data cannot be recorded on the same disc.
The two head system of (2) above can record edited data on the same disc in real time. This system, however, requires an extra optical head for reproduction only accompanied by its peripheral circuit. This makes the circuit complicated and increases the manufacturing cost.
It is, therefore, a second object of the invention to provide an apparatus for recording and reproducing a signal on a disc type recording medium capable of performing editing of recorded data with a standard set of recording and reproducing heads only.
An MD player generally has a function, as one of its standard functions, of recording and reproducing a two-channel music signal. In a case where it is desired to realize recording and reproduction of a four-channel music signal with this type of MD player, it is conceivable (1) to operate two MD players using a single common disc with the same master clock so that one MD player will record and reproduce signals of first and second channels and the other MD player will record and reproduce signals of third and fourth channels in synchronism with each other, or (2) to adopt a special format which is different from a standard format to record and reproduce a four-channel signal with a single MD player.
The two player system of (1) above, however, is expensive because it requires two players and, moreover, the circuit as a whole becomes complex and large.
The special format system of (2) above cannot be carried out under the current standard and, moreover, such system will not be compatible with a normal MD player using a standard format.
It is, therefore, a third object of the invention to provide an apparatus for recording and reproducing a signal on a disc type recording medium which, notwithstanding that it has a function of recording and reproducing only a two-channel signal and uses only a standard format, is capable of recording and reproducing a four-channel signal with only a pair of recording and reproducing heads.
For dubbing data from one disc to another by using an optical disc type recording and reproducing apparatus, a double-deck type device is generally proposed according to which data is read from a reproduction only disc by a reproduction only deck and this data is recorded in a recording disc by a different recording only deck. This double-deck type device is actually used in the field of the Compact Cassette. For realizing the double-deck type device in an optical disc type recording and reproducing device such as an MD player, however, circuits as shown in FIGS. 18 and 19 are required.
The circuit of FIG. 18 is based on a general disc recording and reproducing type MD deck. In FIG. 18, reference character 41 designates a disc, 42 a spindle motor for rotating this disc 41 at a constant linear velocity, 43 an optical pick-up for optically reading information from the disc 41 or magneto-optically writing information on the disc 41, 44 a feed motor for moving this pick-up 43 in the radial direction of the disc 41, 45 a high frequency (RF) amplifier for amplifying the output of the pick-up 43 and 46 a servo control section for peforming a rotation control for the spindle motor 42, a feed control for the feed motor 44 and a focus tracking control for the pick-up 43.
A reading system of this MD player includes an EFM decoder section of an EFM encoder/decoder 47 for decoding the output of the amplifier 45, an address decoder 48 for detecting, from the output of the amplifier 45, an address of data being reproduced, a memory 49 for temporarily storing the decoder output of the EFM encoder/decoder 47, a controller 50 for the memory 49, an audio compression decoder section of an audio compressor encoder/decoder 41 for expanding the output of the memory 49, and a digital-to-analog converter 52 for converting the expansion output of the audio compression decoder section to an analog signal.
The EFM encoder/decoder 47 adopts EFM (eight to fourteen modulation) as its modulation system and CIRC (cross interleave Reed-Solomon code) as its error correction system.
A writing system of this MD player includes an analog-to-digital conversion section 53 for converting an analog signal to a digital signal, an encoder section of the audio compressor encoder/decoder 51 for compressing the converted digital signal for removing an unnecessary component for reproduction of an audio signal from the digital signal, the memory 49 for temporarily storing compressed signal and the controller 50 for the memory 49, an EFM encoder section of the EFM encoder/decoder 47 fOF EFM modulating the output of the memory 49, a recording head (magnetic head) 54 for writing the encoded signal on the disc 41 in association with the optical pick-up 43.
There are also provided a system controller 56 which controls the entire MD player, a display 57 which displays various information and operation keys 58 which impart various instructions.
For constructing a double-deck for dubbing on the basis of the above described recording and reproducing deck, a reproduction only deck as shown in FIG. 19 must be added. The circuit of FIG. 19 includes an optical disc 41R for reproduction, a spindle motor 42R for rotating the disc 41R at a constant linear velocity, an optical pick-up 43R for reading information optically from the disc 41R, a feed motor 44R for moving the pick-up 43R in the radial direction of the disc 41R, a high frequency amplifier 45R for amplifying the output of the pick-up 43R and a servo control section 46R for rotation control of the spindle motor 42R, feed control of the feed motor 44R and focus tracking of the pick-up 43R.
This reproduction only MD player has only a reading system including an EFM decoder 47R for demodulating the output of the amplifier 45R, an address decoder 48R for detecting, from the output of the amplifier 45R, address of data being reproduced, a memory 49R for temporarily storing the decoder output of the EFM decoder 47R and an intermittent reproduction memory controller 50R and an audio compressor decoder 51R for expanding the output of the memory 49R. The reproduction only MD player uses the system controller 56 commonly and supplies the expansion output of the audio compressor decoder 51R to the digital-to-analog converter 52 (for monitoring) or to the audio compressor encoder/decoder 51 for dubbing.
For enabling such double-deck construction, two switches 59 and 60 as shown in FIG. 18 are added. The first switch 59 is provided for selecting input to the digital-to-analog converter 52. The switch 59 selects, in the illustrated state, the expansion data read from the reproduction only disc 41R and, when the switch 59 is connected to the other side, selects the expansion data read from the recording and reproduction disc 41. The second switch 60 is provided for selecting input to the audio compressor encoder/decoder 51R. The illustrated state shows a dubbing mode in which the switch 60 selects the output of the audio compressor decoder 51R. When the first switch 59 is connected in the illustrated state in the dubbing mode, monitoring can be made simultaneously. When the switch 60 is connected to the other side, the output of the analog-to-digital converter 53 is selected so that the mode becomes a normal recording mode in which audio input from outside is recorded in the recording and reproduction disc 41.
The above described double deck structure is based on the concept that a reproduction only deck is provided in addition to a recording and reproducing deck and, accordingly, component parts for two decks are required for most component parts excluding few component parts such as the digital-to-analog converter 52, analog-to-digital converter 53 and system controller 56. This requires a very complex circuit which increases the manufacturing cost. Particularly, the circuit requires two optical pick-ups which are indispensable for an optical disc and the optical pick-up is very expensive compared with a magnetic head used for a Compact Cassette so that it is difficult to avoid increase in the manufacturing cost.
It is, therefore, a fourth object of the invention to provide an apparatus for recording and reproducing a signal on a disc type recording medium which is capable of dubbing data from a reproducing optical disc to a recording optical disc by using a single recording and reproducing deck and particularly using a single optical pick-up.